Accelerating effect of hydrocortisone on the keratinization of chick embryonic skin growing in a chemically defined medium

In an attempt to examine histologically, chemically and biochemically the effect of hydrocortisone in a minimal concentration on keratinization of 13-day chick embryonic shank skin, a simple replicate culture method (‘Millipore’ filter-roller-tube method) was devised to cultivate rather large pieces of the skin in a chemically defined medium, BGJb supplemented with ascorbate. Hydrocortisone added in a minimal concentration of 0·001 μg/ml produced a heavily cornified eosinophilic layer over the epidermis after 4 days' cultivation, whereas in the absence of the steroid no sign of cornification could be found during culture. Determination of total protein and analysis of amino acid composition of whole protein of the epidermis indicated that hydrocortisone accelerated epidermal cornification as compared with in ovo development. Pregnenolone and progesterone showed no effect on the in vitro keratinization of the epidermis and deoxycorticosterone gave a slight effect: thus the cornification-accelerating effect of hydrocortisone seems to be attributable to its glucocorticoid activity.